The invention relates to coloured or pigmented bituminous materials, notably used as covering, siding or sealing materials.
A method for the colouring or the pigmenting of bituminous materials has already been described in French Patent No. 2 352 929.
It consists of applying a colouring composition onto a fibrous material, then drying the composition and then impregnating the fibrous material coated in this way, in a bath of hot bitumen.
The colouring composition has a high water content and comprises resin, pigments, a thickening agent, a dispersing agent and possibly fillers.
This method allows one to obtain coloured bituminous materials whose resistance to ageing is better than that observed with materials obtained by known methods.
However, it is apparent that it is necessary to further improve the resistance to ageing of coloured bituminous materials in order to prevent their degradation, including even under extreme climatic conditions.
Firstly the invention relates to a new composition based on resin and pigments, for obtaining coloured bituminous materials.
The resin used has the particular property of having a restricted range of solubility.
The colouring composition is prepared by carrying out the following successive steps:
Firstly, the resin is dissolved in water and within its range of solubility. The percentages by weight of resin and of water in the mixture obtained are between about 30 and 70% of resin and 30 and 70% of water. The mixture obtained is clear.
The additive that enables one to obtain a stable dispersion, is added to the mixture. The quantity of additive is between about 0.5 and 3% of the weight of the resin.
The additive is a surfactant, the molecule of which includes a chain with hydrophilic character and a chain with hydrophobic character. It is an amphiphilic type of product.
Then water is added to the mixture in solution in sufficient quantity to cause the resin to precipitate. In effect, because of the addition of the water, the resin is no longer within its range of solubility.
The additive allows the dispersion of the resin in the water to be stabilised, and when the water is added to the mixture prevents the setting and the agglomeration of the precipitated particles of resin which would end up in a gel.
Finally, pigments are introduced into the mixture to obtain the colouring composition according to the invention. The pigments are in powder form, with a particle size of between 0.5 and 50 xcexcm. They are of an organic or a mineral type.
The quantity of pigments is between 50 and 150% of the weight of the resin.
The colouring composition according to the invention therefore has:
between about 5 to 20% and preferably 15% by weight of a resin with a restricted solubility range
between about S to 40% and preferably 20% by weight of pigments,
between about 0.1 to 5% and preferably 1% by weight of an additive with respectively hydrophilic and hydrophobic properties,
between about 90 to 60% and preferably 64% by weight of water.
The invention also relates to a method of obtaining coloured or pigmented bitminous materials.
This method consists first of all of applying, onto at least one surface of the fibrous material to be treated, the colouring composition that has just been described.
The fibrous material is notably a cellulose based felt or a board. It can be in the dry state or may include water in an amount ranging up to 60% by weight.
The composition can be applied notably by spraying with or without compressed air, by coating the surface using at least one transfer roller (made of foam for example) or by the deposition of a very thin film.
The thickness of the layer obtained corresponds to a coating weight of dry material between about 25 to 130 g/m2.
Within this range of values, the thickness of the layer of colouring composition is sufficient to colour the substrate and remains thin enough to allow subsequent penetration of the bitumen into the fibrous material.
The coloured fibrous material is then dried, notably by simple drying in air. It is finally subjected to a bitumen impregnation operation, the layer of colouring composition undergoing curing at high temperature, within the mass of hot bitumen.
The bituminous material obtained has colouring on its surface. Tests carried out have shown that this colouring has better appearance and resistance compared with that provided using traditional colouring methods.